feat: impl eth_syncing (#104)

* eth_api: Implement syncing method

* tests: test eth_syncing

* docs: mark eth_syncing as SUPPORTED

* docs: add eth_syncing to test_endpoints.http

* docs: add example for eth_syncing

SUPPORTED_APIS.md

@@ -70,7 +70,7 @@ The `status` options are:
 | `ETH` | `eth_submitHashrate` | `NOT IMPLEMENTED` | Used for submitting mining hashrate |
 | `ETH` | `eth_submitWork` | `NOT IMPLEMENTED` | Used for submitting a proof-of-work solution |
 | `ETH` | `eth_subscribe` | `NOT IMPLEMENTED` | Starts a subscription to a particular event |
-| `ETH` | `eth_syncing` | `NOT IMPLEMENTED`<br />[GitHub Issue #49](https://github.com/matter-labs/era-test-node/issues/49) | Returns an object containing data about the sync status or `false` when not syncing |
+| [`ETH`](#eth-namespace) | [`eth_syncing`](#eth_syncing) | `SUPPORTED` | Returns an object containing data about the sync status or `false` when not syncing |
 | `ETH` | `eth_uninstallFilter` | `NOT IMPLEMENTED`<br />[GitHub Issue #38](https://github.com/matter-labs/era-test-node/issues/38) | Uninstalls a filter with given id |
 | `ETH` | `eth_unsubscribe` | `NOT IMPLEMENTED` | Cancel a subscription to a particular event |
 | `EVM` | `evm_addAccount` | `NOT IMPLEMENTED` | Adds any arbitrary account |
@@ -683,6 +683,30 @@ curl --request POST \
 }'
 ```
 
+### `eth_syncing`
+
+[source](src/node.rs)
+
+Returns syncing status of the node. This will always return `false`.
+
+#### Arguments
+
++ _NONE_
+
+#### Status
+
+`SUPPORTED`
+
+#### Example
+
+```bash
+curl --request POST \
+  --url http://localhost:8011/ \
+  --header 'content-type: application/json' \
+  --data '{"jsonrpc": "2.0","id": "1","method": "eth_syncing","params": []
+}'
+```
+
 ## `HARDHAT NAMESPACE`
 
 ### `hardhat_setBalance`

src/node.rs

@@ -1715,7 +1715,7 @@ impl<S: Send + Sync + 'static + ForkSource + std::fmt::Debug> EthNamespaceT for
         &self,
     ) -> jsonrpc_core::BoxFuture<jsonrpc_core::Result<zksync_basic_types::web3::types::SyncState>>
     {
-        not_implemented("syncing")
+        Ok(zksync_basic_types::web3::types::SyncState::NotSyncing).into_boxed_future()
     }
 
     fn accounts(
@@ -1765,3 +1765,17 @@ impl<S: Send + Sync + 'static + ForkSource + std::fmt::Debug> EthNamespaceT for
         not_implemented("fee history")
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use crate::{http_fork_source::HttpForkSource, node::InMemoryNode};
+    use zksync_core::api_server::web3::backend_jsonrpc::namespaces::eth::EthNamespaceT;
+    use zksync_web3_decl::types::SyncState;
+
+    #[tokio::test]
+    async fn test_eth_syncing() {
+        let node = InMemoryNode::<HttpForkSource>::default();
+        let syncing = node.syncing().await.expect("failed syncing");
+        assert!(matches!(syncing, SyncState::NotSyncing));
+    }
+}

test_endpoints.http

@@ -265,6 +265,17 @@ content-type: application/json
 POST http://localhost:8011
 content-type: application/json
 
+{
+    "jsonrpc": "2.0",
+    "id": "2",
+    "method": "eth_syncing",
+    "params": []
+}
+
+###
+POST http://localhost:8011
+content-type: application/json
+
 {
     "jsonrpc": "2.0",
     "id": "2",